Shared psychotic disorder is a very rare condition in which people
close to a mentally ill person share his or her false beliefs
(delusions). As an example, a man with schizophrenia may falsely
believe that his children are trying to murder him. His wife develops
shared psychotic disorder and comes to believe it as well. This
disorder usually occurs in long-term relationships and involves
two people. However, it can also develop among members of a group,
such as within families. It affects women more often than men.

Aside from the delusions, the thoughts and behavior of people
with shared psychotic disorder are usually fairly normal.

Someone who is closely associated with a delusional person also
develops a delusion.

The content of this new delusion is similar to that of the first
person's delusion.

The disorder is not explained better by another psychotic disorder,
such as Schizophrenia
or Mood Disorder
with Psychotic Features.

This disorder is not directly caused by a general medical condition
or the use of substances, including prescription medications.

Some disorders
have similar or even the same symptom. The clinician, therefore,
in his diagnostic attempt has to differentiate against the following
disorders which he needs to rule out to establish a precise
diagnosis.